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Thread Subject:
Matrix with symbol

Subject: Matrix with symbol

From: Yi

Date: 9 Mar, 2008 05:45:05

Message: 1 of 5

When I want a matrix with symbol, like below:
>> syms a b c
>> A=[a b c]'
 
A =
 conj(a)
 conj(b)
 conj(c)

>> A=[a;b;c]
 
A =
 a
 b
 c

What's wrong with the first method? What is the physical
meaning of conj(a)? If I want to do furthur calculation,
the first method desn't work. I have to input under the
second method. Could Any body tell me what's wrong?

Thanks & Best Regards

Subject: Matrix with symbol

From: Bruno Luong

Date: 9 Mar, 2008 08:44:02

Message: 2 of 5

"Yi " <hvachy@163.com> wrote in message
<fqvth1$a5i$1@fred.mathworks.com>...
> What is the physical
> meaning of conj(a)?

No physical meaning. conj means conjuguate.

Bruno

Subject: Matrix with symbol

From: Philip Jonas

Date: 9 Mar, 2008 10:45:04

Message: 3 of 5

You have to use the second way to define a matrix. The command
"conj(X)" gives you the complex conjugate of X. You will
find that by typing in matlab command window "help conj".

Subject: Matrix with symbol

From: roberson@ibd.nrc-cnrc.gc.ca (Walter Roberson)

Date: 9 Mar, 2008 16:37:58

Message: 4 of 5

In article <fqvth1$a5i$1@fred.mathworks.com>, Yi <hvachy@163.com> wrote:
>When I want a matrix with symbol, like below:
>>> syms a b c
>>> A=[a b c]'

>A =
> conj(a)
> conj(b)
> conj(c)

' means complex conjugate. Try

A=[a b c].'

.' means transpose.
--
  "No sincere artist was ever completely satisfied with his labour."
                                              -- Walter J. Phillips

Subject: Matrix with symbol

From: Steven Lord

Date: 10 Mar, 2008 02:13:37

Message: 5 of 5


"Yi " <hvachy@163.com> wrote in message
news:fqvth1$a5i$1@fred.mathworks.com...
> When I want a matrix with symbol, like below:
>>> syms a b c

When you define symbolic variables like this, the toolbox doesn't make any
assumption about what values those variables may eventually represent. So
...

>>> A=[a b c]'

it has to take into account the possibility that a, b, and/or c could
represent complex values. So when you use ' (the CTRANSPOSE operator,
otherwise known as the complex conjuate transpose) the result is the
conjugate of the transposed vector, or exactly what you wrote below.

> A =
> conj(a)
> conj(b)
> conj(c)
>
>>> A=[a;b;c]
>
> A =
> a
> b
> c

No complex conjugate transpose, no conjugate elements in the resulting
vector.

> What's wrong with the first method? What is the physical
> meaning of conj(a)? If I want to do furthur calculation,
> the first method desn't work. I have to input under the
> second method. Could Any body tell me what's wrong?

If you want to tell the toolbox that a, b, and c are real, use:

syms a b c real
isAequaltoAtranspose = a == a'
A = [a b c]'

--
Steve Lord
slord@mathworks.com

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